Relative atomic mass and Atomic mass unit

                                  Atomic mass unit

Introduction:

Avagadro is a person  who in 1811 , suggested that atomic mass and molecular masses could be expressed on an atomic mass scales. This scales is based on the comparison between atomic mass and molecular mass with the mass of a reference atom

Atomic mass unit  is the mass equal 1/12 units of the mass of

 a  ₆¹²C  atoms because ₆¹²C  isotopes has been assigned an atomic mass of 12 unit exactly.

Representation:    

                                        It is represented by amu.

 1 amu = µ=Mass of atom/12

Absolute mass of a   ₆¹²C   atom = 1.9924 X 10^-23g

1 amu = µ =1.9924 X 10^-23g/12

          =1.66 X 10^-24g

          =1.66 X 10^-27Kg

                               Relative atomic mass

The Relative atomic mass of an element is defined as mass an atom of an element compared with the mass of an atom of carbon  ¹²C   
taken as 12.

It is a pure number and have no units .

 The Relative atomic mass indicates the number of times that element is heavier than 1/12 of a ¹²C   atom.